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| Rice performance at 105 days after planting subjected to three phosphorus treatments (No P amendment (-P), two rates of micro-dose placement (MICRO P), and a conventional broadcast (+P)) grown under submerged conditions on a P-deficient lowland. (Photos courtesy : Pieterjan De Bauw.) |
Lowland rice production in
sub-Saharan Africa (SSA) is often limited by water supply and low soil
phosphorus (P) availability and efforts are needed towards more efficient
management of both resources.
Additionally, crop roots
are highly important for both water and P acquisition from the soil, and hence
root performance plays a critical role determining water and P use efficiency.
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| Rice performance at 105 days after planting subjected to three phosphorus treatments (No P amendment (-P), two rates of micro-dose placement (MICRO P), and a conventional broadcast (+P)) grown under field capacity on a P-deficient lowland. |
Field and pot experiments
were set up to evaluate combinations of water saving technologies (such as
alternate wetting and drying, and aerobic rice) and P placement methods (i.e.
the localized application of a small P fertilizer dose to a sub-surface area,
often combined with seeds into the planting hole) with due attention to
treatment effects on root architecture.
P applied to soil as
fertilizer moves away from the point of application mainly through diffusion,
while sorption and precipitation reactions may reduce its mobility and
availability to plants. Therefore, P diffusion and sorption outwards
contrasting application rates of P placements was modeled under different water
regimes to assess the combined effects on P availability to the rice crop.
It was shown that reduced
water supply (i.e. at field capacity compared to soil saturation) restricted P
diffusion, hence reduced P immobilization, and so increased total P
availability from placements. These differences between water treatments were
more pronounced at lower than at higher P supply and were confirmed on the
field.
This study, which was carried
out by scientists from Catholic University of Leuven, International Potato
Center (CIP) and Africa Rice Center (AfricaRice), shows that both root responses
and P diffusion outwards placed granules explain rice development and yields
under P placement and water saving technologies. Obviously, broadcasting a
large P rate remains advisable under P deficiency, but resource limitations may
hamper such amendments.
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| Establishing a field experiment on a P deficient lowland in Tanzania. |
“We argue, therefore, that
P placements can contribute to intensify lowland rice production while
countering soil P declines in P deficient lowlands,” explained Dr Pieterjan De
Bauw, Division of Soil and Water Management, Catholic University of Leuven, who
led the study.
“Without P application or
when applying small P placement rates, interactions with water management
should definitely be considered as water saving technologies were observed to
enhance P uptake, enhance rice development, and increase yields in such
situations,” he added.
The findings of the study
were revealed in the article “Combining phosphorus placement and water saving
technologies enhances rice production in phosphorus-deficient lowlands” by De
Bauw P., Vandamme E., Senthilkumar K., Lupembe A., Smolders E., Merckx R.,
published in the journal Field Crops Research, 236, 177-189.
